Sea urchins

class of marine invertebrates

The subclass Euechinoidea includes almost all living species of sea urchin, with fossil forms going back as far as the Triassic.

Perischoechinoidea is a subclass of primitive sea urchins that were abundant in the Palaeozoic seas. However, the great majority of species died out during the Mesozoic, as the more advanced euechinoid sea urchins became common. Today, only a single order, the Cidaroida, survives.

The Atelostomata are a type of sea urchins. They are distinguished from other sea urchins by their irregular shape and the absence of a feeding lantern. The group includes the well known heart urchins, as well as some less familiar and extinct forms.

hard shell of some spherical marine animals, notably sea urchins and microorganisms such as testate foraminiferans, radiolarians, and testate amoebae

The Diadematacea are a superorder of sea urchins. Unlike most other sea urchins, they generally have hollow spines. The tubercles on their tests are perforated, and most species possess gills.

The Holectypoida are an order of sea urchins related to the sand dollars. The order consists of just two living genera, but was once more diverse.

Stomopneustoida is an order of echinoderms belonging to the class Echinoidea.

Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.

The Neognathostomata are a superorder of sea urchins.

Euptagus is a genus of sea urchins. It is in the family Eupatagidae.

superorder of sea urchins

The infraclassis Carinacea includes most living species of regular sea urchin, and fossil forms going back as far as the Triassic.

Echinoneoida is an order of echinoderms belonging to the class Echinoidea.

genus of echinoderms

Scutellidae is a family of sea urchins in the superfamily Scutelloidea. All genera except Scaphechinus are extinct.